Windows 3.1.031 is mentioned in an internal Microsoft e-mail from 1991-07.. The e-mail first discusses the performance of Microsoft's new disk caching program called SmartDrive (codenamed Bambi) compared to other popular disk caching programs at the time. The e-mail then also shows results from comparing performance of this build to pre-release versions of IBM's OS/2 2.0. Results for version 6.138 were already available, while tests were being performed on version 6.149 at the time the e-mail was written. The results indicate Windows 3.1 performed better than OS/2 2.0 in most tests.